[FrameworkBundle] Add extra attribute for HttpClient Configuration

[voodooism]

Q	A
Branch?	6.3
Bug fix?	no
New feature?	yes
Deprecations?	no
License	MIT
Doc PR	coming soon...

I want to configure HttpClient once in configure file and forget about the configuration when doing a request or injection. In my particular case, I want to pass certificates to the client as raw values using special curlopts. Here #48775 proposed the best way to do it - using extra attribute in configuration.

It's going to look like so

return static function (FrameworkConfig $frameworkConfig): void {
    $httpClient = $frameworkConfig->httpClient();
    $httpClient->defaultOptions([
        'extra' => ['curl' => ['foo' => 'bar']]
    ]);

    $httpClient->scopedClient('some_client')
        ->baseUri('https://some.uri')
        ->header('Accept', 'application/json')
        ->extra(['curl' => ['foo' => 'bar']]);
}

[nicolas-grekas]

LGTM thanks!

[OskarStark]

Please add some documentation against, thanks

[fabpot]

Thank you @voodooism.